The Harvard Medical School-based research training program entitled Infectious Diseases and Basic Microbiological Mechanisms offers a minimum of two years of laboratory-based research training for physicians and postdoctoral PhD scientists. The aim is to provide substantive research training experience with relevant supporting course work and thereby to enable the postdoctoral trainee to become an independent investigator in the fields of infectious diseases and microbiology. Training laboratories are in nine major areas: (1) bacteriology, including pathogenesis, genetics, toxins, virulence factors, cell biology, host defense, and vaccine development; (2) virology, including pathogenesis, genetics, cell biology, virulence, host defense, antiviral agents, and retrovirology; (3) parasitology, including pathogenesis, chloroquine resistance of malaria, parasite-cell interactions, and host defense; (4) immunology, including complement, T cells, B cells, and regulation of the antibody response; (5) epidemiology, including pharmacoepidemiology and nosocomial infections; (6) cell biology of eosinophils and basophils; (7) biochemistry of proteins, carbohydrates, and lipids; (8) molecular biology and genetics; and (9) biodefense and emerging infectious diseases. The purpose of this renewal application for this T32 grant is the continuation of this highly successful program, which has been supported by the NIH for the past 30 years. During the past five-year period, approximately 248 trainees completed the program. Of these individuals, 175 now hold positions in academia or work in government service. Sixty hold the rank of assistant professor or higher at 52 colleges, universities and medical schools around the world. An additional 36 have taken positions as scientists in industry. Thirteen are identified as practicing physicians many of whom also hold academic appointments. Although only eight positions per year are supported by this grant, 191 postdoctoral trainees are currently being funded by our, training program in the laboratories of the 51 participating research mentors.